Yuan
Dongliang
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Dongliang
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ArticleA Maluku Sea intermediate western boundary current connecting Pacific Ocean circulation to the Indonesian Throughflow(Nature Research, 2022-04-19) Yuan, Dongliang ; Yin, Xueli ; Li, Xiang ; Corvianawatie, Corry ; Wang, Zheng ; Li, Yao ; Yang, Ya ; Hu, Xiaoyue ; Wang, Jing ; Tan, Shuwen ; Surinati, Dewi ; Purwandana, Adi ; Wardana, Adhitya Kusuma ; Ismail, Mochamad Furqon Azis ; Budiman, Asep S. ; Bayhaqi, Ahmad ; Avianto, Praditya ; Santoso, Priyadi Dwi ; Kusmanto, Edi ; Dirhamsyah, Dirham ; Arifin, Zainal ; Pratt, Lawrence J.The Indonesian Throughflow plays an important role in the global ocean circulation and climate. Existing studies of the Indonesian Throughflow have focused on the Makassar Strait and the exit straits, where the upper thermocline currents carry North Pacific waters to the Indian Ocean. Here we show, using mooring observations, that a previous unknown intermediate western boundary current (with the core at ~1000 m depth) exists in the Maluku Sea, which transports intermediate waters (primarily the Antarctic Intermediate Water) from the Pacific into the Seram-Banda Seas through the Lifamatola Passage above the bottom overflow. Our results suggest the importance of the western boundary current in global ocean intermediate circulation and overturn. We anticipate that our study is the beginning of more extensive investigations of the intermediate circulation of the Indo-Pacific ocean in global overturn, which shall improve our understanding of ocean heat and CO2 storages significantly.
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ArticleHydraulics and mixing of the deep overflow in the Lifamatola Passage of the Indonesian Seas(American Meteorological Society, 2020-09-01) Tan, Shuwen ; Pratt, Lawrence J. ; Yuan, Dongliang ; Li, Xiang ; Wang, Zheng ; Li, Yao ; Corvianawatie, Corry ; Surinati, Dewi ; Budiman, Asep S. ; Bayhaqi, AhmadHydrographic measurements recently acquired along the thalweg of the Lifamatola Passage combined with historical moored velocity measurements immediately downstream of the sill are used to study the hydraulics, transport, mixing, and entrainment in the dense overflow. The observations suggest that the mean overflow is nearly critical at the mooring site, suggesting that a weir formula may be appropriate for estimating the overflow transport. Our assessment suggests that the weir formulas corresponding to a rectangular, triangular, or parabolic cross section all result in transports very close to the observation, suggesting their potential usage in long-term monitoring of the overflow transport or parameterizing the transport in numerical models. Analyses also suggest that deep signals within the overflow layer are blocked by the shear flow from propagating upstream, whereas the shallow wave modes of the full-depth continuously stratified flow are able to propagate upstream from the Banda Sea into the Maluku Sea. Strong mixing is found immediately downstream of the sill crest, with Thorpe-scale-based estimates of the mean dissipation rate within the overflow up to 1.1 × 10−7 W kg−1 and the region-averaged diapycnal diffusivity within the downstream overflow in the range of 2.3 × 10−3 to 10.1 × 10−3 m2 s−1. Mixing in the Lifamatola Passage results in 0.6–1.2-Sv (1 Sv ≡ 106 m3 s−1) entrainment transport added to the overflow, enhancing the deep-water renewal in the Banda Sea. A bulk diffusivity coefficient estimated in the deep Banda Sea yields 1.6 × 10−3 ± 5 × 10−4 m2 s−1, with an associated downward turbulent heat flux of 9 W m−2.
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ArticleOcean observations to improve our understanding, modeling, and forecasting of subseasonal-to-seasonal variability(Frontiers Media, 2019-08-08) Subramanian, Aneesh C. ; Balmaseda, Magdalena A. ; Centurioni, Luca R. ; Chattopadhyay, Rajib ; Cornuelle, Bruce D. ; DeMott, Charlotte ; Flatau, Maria ; Fujii, Yosuke ; Giglio, Donata ; Gille, Sarah T. ; Hamill, Thomas M. ; Hendon, Harry ; Hoteit, Ibrahim ; Kumar, Arun ; Lee, Jae-Hak ; Lucas, Andrew J. ; Mahadevan, Amala ; Matsueda, Mio ; Nam, SungHyun ; Paturi, Shastri ; Penny, Stephen G. ; Rydbeck, Adam ; Sun, Rui ; Takaya, Yuhei ; Tandon, Amit ; Todd, Robert E. ; Vitart, Frederic ; Yuan, Dongliang ; Zhang, ChidongSubseasonal-to-seasonal (S2S) forecasts have the potential to provide advance information about weather and climate events. The high heat capacity of water means that the subsurface ocean stores and re-releases heat (and other properties) and is an important source of information for S2S forecasts. However, the subsurface ocean is challenging to observe, because it cannot be measured by satellite. Subsurface ocean observing systems relevant for understanding, modeling, and forecasting on S2S timescales will continue to evolve with the improvement in technological capabilities. The community must focus on designing and implementing low-cost, high-value surface and subsurface ocean observations, and developing forecasting system capable of extracting their observation potential in forecast applications. S2S forecasts will benefit significantly from higher spatio-temporal resolution data in regions that are sources of predictability on these timescales (coastal, tropical, and polar regions). While ENSO has been a driving force for the design of the current observing system, the subseasonal time scales present new observational requirements. Advanced observation technologies such as autonomous surface and subsurface profiling devices as well as satellites that observe the ocean-atmosphere interface simultaneously can lead to breakthroughs in coupled data assimilation (CDA) and coupled initialization for S2S forecasts. These observational platforms should also be tested and evaluated in ocean observation sensitivity experiments with current and future generation CDA and S2S prediction systems. Investments in the new ocean observations as well as model and DA system developments can lead to substantial returns on cost savings from disaster mitigation as well as socio–economic decisions that use S2S forecast information.
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ArticleDetecting change in the Indonesian Seas(Frontiers Media, 2019-06-04) Sprintall, Janet ; Gordon, Arnold L. ; Wijffels, Susan E. ; Feng, Ming ; Hu, Shijian ; Koch-Larrouy, Ariane ; Phillips, Helen E. ; Nugroho, Dwiyoga ; Napitu, Asmi ; Pujiana, Kandaga ; Susanto, R. Dwi ; Sloyan, Bernadette M. ; Yuan, Dongliang ; Riama, Nelly Florida ; Siswanto, Siswanto ; Kuswardani, Anastasia ; Arifin, Zainal ; Wahyudi, A’an J. ; Zhou, Hui ; Nagai, Taira ; Ansong, Joseph ; Bourdalle-Badié, Romain ; Chanut, Jerome ; Lyard, Florent ; Arbic, Brian K. ; Ramdhani, Andri ; Setiawan, AgusThe Indonesian seas play a fundamental role in the coupled ocean and climate system with the Indonesian Throughflow (ITF) providing the only tropical pathway connecting the global oceans. Pacific warm pool waters passing through the Indonesian seas are cooled and freshened by strong air-sea fluxes and mixing from internal tides to form a unique water mass that can be tracked across the Indian Ocean basin and beyond. The Indonesian seas lie at the climatological center of the atmospheric deep convection associated with the ascending branch of the Walker Circulation. Regional SST variations cause changes in the surface winds that can shift the center of atmospheric deep convection, subsequently altering the precipitation and ocean circulation patterns within the entire Indo-Pacific region. Recent multi-decadal changes in the wind and buoyancy forcing over the tropical Indo-Pacific have directly affected the vertical profile, strength, and the heat and freshwater transports of the ITF. These changes influence the large-scale sea level, SST, precipitation and wind patterns. Observing long-term changes in mass, heat and freshwater within the Indonesian seas is central to understanding the variability and predictability of the global coupled climate system. Although substantial progress has been made over the past decade in measuring and modeling the physical and biogeochemical variability within the Indonesian seas, large uncertainties remain. A comprehensive strategy is needed for measuring the temporal and spatial scales of variability that govern the various water mass transport streams of the ITF, its connection with the circulation and heat and freshwater inventories and associated air-sea fluxes of the regional and global oceans. This white paper puts forward the design of an observational array using multi-platforms combined with high-resolution models aimed at increasing our quantitative understanding of water mass transformation rates and advection within the Indonesian seas and their impacts on the air-sea climate system. Introduction